Sacred functions in which clergy and people go in parade from one sacred place to another. They may be conducted entirely within the church or may take place outside the confines of the building; even from one church to another. Their object is public supplication to God for some determined favor. They stir the faith of the pious to acts of piety; procure for participants great blessings from God; and give thanks to the Almighty for His favors. Ordinary processions are those assigned to certain days, as those on Palm Sunday, Holy Thursday, Good Friday, and Corpus Christi, or to certain functions as at the consecration of churches. They are prescribed either by the liturgy, the Code of Canon Law, or decree of the bishop for a determined public cause, yet recurring by custom. Extraordinary processions are ordered in certain calamities or as thanksgiving for some signal favor. The decreeing of these extraordinary processions is by the bishop or at least with his sanction. The Roman Ritual admonishes the priests in charge of processions, either ordinary or extraordinary, duly to instruct the faithful of the time at which the procession is to be held and the order to be followed in it. The Ritual likewise gives the order of precedence for those taking part in the function. The cross, emblem of faith, should always be at the head of the procession. Other banners may be used if they are ornamented with religious designs or pictures. Processions of the Blessed Sacrament are a popular expression of devotion to the Blessed Sacrament.